The present invention relates to an apparatus and method for heating air and more particularly to an improved arrangement for indirect fired air heating with portable structure uniquely suitable to heat personnel and equipment under field conditions.
In the fluid heating art, it has been generally known for a number of years to deliver combustion air from several locations in a combustion chamber to facilitate combustion within such chamber, attention being directed to the long since expired U.S. Pat. Nos. 585,792, issued to M. T. Russell on July 6, 1897; to 615,445, issued to C. M. Gearing on Dec. 6, 1898; and, to 741,504, issued to W. Kemp on Oct. 13, 1903. All three of these expired patents teach such principle of multiple air introduction into a furnace combustion chamber as being old in the art. Attention further is directed to more recent U.S. Pat. Nos. 2,440,491, issued to E. F. Schwander on Apr. 27, 1948 and 2,464,791, issued to C. A. Bonvillian et al on Mar. 22, 1949, both patents teaching introducing air along several points of a combustion chamber with the Schwander patent introducing air from opposed combustion chamber points and the Bonvillian patent suggesting secondary air be delivered along elongated openings of a chamber under any pressure. This broad principle of utilizing primary and opposed secondary air ducts in a combustion chamber has even been employed in the hot water boiler art with known General Electric type boilers using such principle to heat water in a shell type water jacket surrounding a combustion chamber. In these aforenoted arrangements, little attention was given to the exhaust products emitted from the fuel burning combustion chamber with such products generally being passed to ambient. More recently, prior art arrangements have been utilized wherein exhaust products emitted from a combustion drum are passed through a heat exchanger extending in an area between the drum and the outer housing in order to capture additional heat in an air stream to be heated in such area, attention being directed to unexpired U.S. Pat. No. 4,729,365, issued to Paul A. Mutchler on Mar. 8, 1988.
The present invention recognizing the heating efficiency accomplished by utilizing exhaust emissions to further heat an air stream as taught by U.S. Pat. No. 4,729,365, employs such known principle in combination with the known principle of delivering combustion supporting air from several locations in a combustion chamber in a novel arrangement that results in even more efficient air stream heating by intensifying the heat to the air stream along an extended area covering a substantial portion of the length of the heat emitting combustion drum and the exhaust products heat exchanger functionally associated with such combustion drum.
In accordance with the present invention, a novel air stream heating arrangement is provided which, recognizing known principles in the heating art, combines these principles in an arrangement which provides a unique method for efficiently heating an air stream with a minimum of steps and an apparatus which can be manufactured and assembled with a minimum of parts and ducting to provide an improved air heater which is light in weight for ready portability and which can be readily and stably disposed in the confines to be heated to occupy a minimum of space for easy usage under varying field conditions. Moreover, the present invention allows the heating of comparatively large volumes of air over large ambient temperature ranges by both radiation and convection with minimum power inputs and with minimum operating noise levels. In addition, the present invention provides for ready access to the burner assembly with minimum carbon production on combustion drum walls due to the nature of combustion and exhaust gas flows with exhaust gases being relatively free of smoke and with emission of such exhaust gases from the confined areas to be heated at ground level.
Various other features of the present invention will become obvious to one skilled in the art upon reading the disclosure set forth herein.